In Texas it is illegal to drive the speed limit in the left lane... if you are impeding other traffic. Even if both vehicles are WAY above the speed limit. Driving the speed limit is NOT a defense to prosecution. Unfortunately most asshats don't know this and believe they have a "right" to the left lane. Driving a motor vehicle in Texas is also a privilege and NOT a right.
On the flip side don't know what the law is where you are. However, hope you gave them ample time and opportunity to move out of the way. Here it's illegal to impede traffic (driving too slow). Unless it is as fast as you feel you can safely navigate the road (again, slow traffic move right if more than one lane).
On another note, we've had many ice storms here over the years (for Texas anyway), and I've never had a problem. Then again I've always owned performance AWD and 4WD vehicles, and did not out drive their capabilities.